Amplifier system and method



June 27, 1933. E. F. CARTER AMPLIFIER SYSTEM AND METHOD Filed Aug. 11 1931' BY z a":

ATTORNEY Lin Patented June 27, 1933 1 toNiTEn mi sm orrica nmiunrr FiNLEY CARTER, or LAUBELTON, NEWEiORK,ASS1G1\TOR To Um'rnn.

RESEARCH CORPORATION, or none ISLAND crrv, nnwyonme oonronerrouor V o DELAWARE mrmrinn sYs'rEM Ann mn'rnon Application filed August 11, 1931. Serial in). 556,384.

This invention relates to amplifier sys-' tems and methods, and particularly to means for changing the amplifying characteristics of an amplifier system.

Radio receiving sets arefrequently built with a-portion adapted to amplifyelectrical vibration at audio frequency, and With'other portions adapted to amplify at rad o frequency; As so constructed, the audio frequency portion often does not provide sufficient amplification for use with a phonograph input. q i V An objectof-this inventionis to adapt-a radio frequency amplifier portion'to use at audio frequencies.

Another 7 object of this v invention is to in terchangeably and'reversibly convert a radio frequency member,or a detector,to an audio frequency amplifier.

till another ob ect a this invention ist'o switch an additional amplifier stage into I the circuit between an audio frequency am- V phonograph pickup. i V A still further object'of this invention is to supply aloud speaker interchangeable at will from aradio signal source, and an audio frequency signal source, while converting forthe latter purpose a, radlo frequency am- 'plifier to operate at audio frequencies.

A still furtherobject of this invention is to switch from a sound Ipickup to a radio pickup by a single switch, which both changesthe source of signals,-changes the number of amplifier stages, and converts a stage fromor to radio and audio frequency operation I A still further ob]ectof lllllS'lIlVGIlillOIl is to switch between a radio frequency signal source and an audio frequency signalsource,

simultaneously converting an amplifier tube stage from detector operation to audio amby the use of a double plifier operation,

and simultaneously-"to convert: a preceding tube system from operation tooperation at audio freuency. o 1

The objects of thisinvention are obtained throw-switch having a plurality of contacts, in combination with thenormal bypass, condensers and o voltage reducing resistors in an amplifierv system.

The double throw switch is adapted to; change the bias upon a detector tube to convert it from a biased detector to a normally biased amplifier, at the same time including an audlo frequency pickup in the grid 01rcult of a preceding tube, with a bypass condenser between the first and second stages switch, in combination with an audio pickup, a radio pickup, an auxiliary bias resistance, voltage reducing resistors, and a plurality ofv bypass condensers, to permit a detector and .last radio stage to be converted to audio stages supplying other audio stages and a loud speaker, whereby the system is adapted to. operate-either with audio frequency or radio frequency sources of signals.

Othereobjects or structural details of this invention will-be apparentfrom the following description when read in connection with the accompanying drawing, wherein F igurel is a circuit diagram of theresential portions of this invention, and

Figure 2 is a diagrammatic representation of a complete radio and phonograph amplifier system according to this invention.

Referring. to the figures, the usual: radio receiver system, may be, provided as shown in detail in Figure 2,including aloud-speaker '1, an'output amplifier stage 2, which may high quality and efliciency ofdetection is desirably equipped with means forproducing the necessaryyalue of C-bias for detection. However, if desired, it may obviously'be equipped with grid leak and condenser for detection. The detector tube 3 has a grid circuit a, consisting of inductance. and capacity. A plurality of radio frequency stages ever, other coupling means maybezutilized.

in the obvious manner. 1

' The radio system may be supplied with power from a rectifier system as shown,or maybe supplied with powenfroi'n aconvenientsource as desired. The system-thus far described is a representative radio receiver system. To theelements ofthissysteinare added. certain other elements in a combinationoutlined in Fig.1, which permits certain of the stages of the radioisystemto be used .foraudioamplification from another pickup to supplythesameoutputamplifier stageand loudspeaker.

These add'ed elemeiits' mayjc'oiisist of in audio-frequency pickup such as aphonograph rs raducer 5-, the output "ofwhich is either directlye'oupledor transmitted through a repeat-mg transformer 6,with a volume control 7 tTheisecehdary of the transroruiergd'is connected in series with the resonant cir 'cuit -8,"to the gridof the last radio amplifier tube mand is adapted to be shunted by a pair of contacts in the double throw, switch ln Radio frequency amplifier stages are custouiiirilyfloperated at lower Voltages than is requiredo n the final output amplifier stages and the excess-voltage is customarily" libsorbed in a. series resistance 1-2, as shown;

Also it is: customary to provide bypass cone densers from the plate lead tothe cathode circuit of both radio frequency amplifieredele'ad through a. resistance 1cm gr tubes "and detector tubes. In "the system shown in the figures these bypass condensers are identified by reference characters 14 and 15; These condensers: are to a common" lead which is adapted to-be connectedthrough another pairof contacts inswitch 11,11) ground, and thereby to-the cathcde cir- FThe necessary rid biasfOr aetecticn in "the detector tube 3, my convenientl be ob mime bythe flow of-eurrentjfi-oiu mind the vine of bins thereby obtained bungee pendent upon the sin-rent flowing-, and the time in ohms-of 'ther'esistunce is; The

#mue of the bins resiasnmimy thus-be controlled by switching in and. out hi the nifc iit an suxilia'iryresistance 17, the 11 when connected iii parallel with "the resis'tance 1s,- opemiiig is reduce the cimiit icsismnee in'ohnis and thereby the voltage drop therethro'ugh efiective 'in pmiucinga bias,

through the-circuits "shown on the grid oft-he tube-'3." The resistanc 17-, ma also beech nec'te'd through contacts in the "switchfl li 5 Intheo 'of' this. s stem, it-

i rudeness-newsman receiver-fin which case signals the I antenna 18,

are inductively transferred to'the grid cirradio frequency stage tube 9, and thereafter transferred through a coupling condenser 24, to'the grid circuit ofthe detector tube 3,

wherein they are further amplified, detected,

and transferred to the output stage 2, for am-- plification andjreproduction in the loud speaker 1.

For this sequence of operations 'itis essential that theswitch '11, be thrown to such a position that the grid circuit 8, of the radio frequency amplifier tube'9, is connected directly to'ground'and the common lead to the bypass condensers 14 and 15is also connected to i Under these conditions the high impedance of the secondary of the transformer 6, is. removed from the grid circuit of the tube 9, whichiis thereby enabled to function atradio frequencies. Simultane; ously the condensers 14 and 15am adapted to operate as bypass condensers. Condenser 11 thus bypasses any reeidualradio frequency from the plate circuit coil of tube'9 to the cathode,and condenser 16 bypasses the necessary radio. frequency in the grid circuit 4, of the tube 3,.to the cathode of tube 3.

For operation with a, onograph pickup position,

The pickup 5, is shown Has im netic reproducer adapted to operate onametoo chanicalphonograph record. It may, however, equally well be alight responsive' member operating with a photographic sound such as is now in commonnse with, sound on film records; alternatively the pickup may be a telegraphone system, a teleofraudio frequency signals.

In the embodiment shown the terminals of phone or telegraph line or any other source 7 the pickup 5, are shunted bya volume control resistance 7, andconnected to a. transformer 6, having anappmpribte ratio and im dance for operation in the grid circuit 0 the tube 9, ltmay be noted that the secondary of the transformer 6, is connected directly in series with the radio frequency circuit 8. The

impedance of the radio circuit toaudio signalsis, however, so -low that the presence of this circuit-is immaterial. Accordingly, the signalpickup from the reproducer 5, isi ad- --v'antagee usly applied to of the tube 9, and the resistance 12, in the plate circuit of the tube 9, is suitable in size and appropriately positioned to operate the tube 9, as a resistance ccupied amplifier. Accordingly,

the output from the-tube 9, passes through the plate coi l of the-tube which likewise is of too low impedance to afiect the audio vibra- .tion to be of consequence,thence through the condensers 14; and 15 which are disconnected from the ground to the grid circuit of the tube 3. Simultaneously, the resistance 17 is connected in parallel with the resistance 16, and the bias produced therethrough reduced to the appropriate value for linear amplification in the tube 3. Aportion of the output from the tube 9, may also passthrough the condenser 24 to the tube 8.

' The audio frequency is thus linearly amplified by the tube 3,'and transferred from it to the output stage tubes in the same manner as the detected radio signals, for reproduction in the loud speaker 1.

Thus the switch 11, m one position permits a radio amplifier stage and a detector to function in the normal fashion, and in another position converts a radio stage and a detector stageto linear audio frequency amplifier stages and connects the source of audio frequency signal vibrations to the tube pre viously operable as a radio frequency amplifier. Thus an amplifier system is enabled to operate at radio frequencies for impedance coupled amplification and detection to the output stage and by means of the transfer switch is also enabled to operate at audio frequency for resistance coupled ampllficavtion to supply the same output stage and loud speaker. 1 g Y The invention above disclosed thus s adapted to operate upon radio frequency s1gnals and upon audio frequency signals with a 7 minimum number of added parts, being es- I sentially only a switch between elements already present plus the necessary signal pickup, and transfer means for the audio signals.

'While there is above disclosedbut a single embodiment of the device of this invention, it is possible to produce still other embodiments without departure from the inventive concept therein disclosed, and it is, therefore, desired that only such limitations shall be imposed upon the appended claims as are stated therein or required by the prior art.

The invention claimed is 1. A sound system'comprising an amplifier member, means adapted to operate said amplifier at radio frequency, and an auxiliary means adapting said amplifier to function alternatively at audio frequencies.

2. A sound system comprlsing a radio frequency amplifier member and an audio frequency amplifier member, and means for frequency amplifier to adapt it to operate alternatively at audio frequencies.

3. A sound system comprising a radio frequency amplifier, a detector and an audio frequency amplifier, and means for converting the radio frequency portion and the detector portion to audio frequency amplifier members.

4. A sound system comprising an amplifier densers connected'thereto, an audio frequency vibration source also connected thereto and a switch. member adapted to shunt said audio frequency source and reconnect said condensers.

'5. The method of operating a vacuum tube amplifier system, which consistsin alternatively connecting or disconnecting a source of audio frequency signals in series with a radioresponsive grid circuit, and simultaneously isolating or grounding bypass condensers between an output circuit and a following stage.

,6. The method of operating a vacuum tube amplifier system, which comprises alternatively amplifying therein radio frequency signals and audio frequency signals, reducing the impedance of an input circuit for said vacuum tube having radio frequency reradio frequency signals, and converting radio frequency bypass condensers to function as audio frequency coupling condensers for said audio signals.

7 The method of operating a vacuum tube amplifier system, which comprises alterna tively amplifying therein radio frequency signals and audio frequency signals,- reducing the impedance of an input circuit for radio means for converting a radio amplifier and a detector of said system into audio frequency amplifiers, comprising means forconnecting a source of audio frequency signals to an input circuit in said amplifier for connecting bypass condensers to function as audio frequency coupling condensers, and for reducing 9. A sound system comprising a plurality of vacuum tube stages having radio frequency impedances associated therewith, a radio fre-- quency coupled condenser therebetween, a voltage reducing resistor, radio frequency by I pass condensers connected therebetween, and a switch member associated therewith adapt.- ed to connect said condensers to ground.

1 0. The method of increasing the number of stages in an audio frequency amplifier con nected to a radio frequency vacuum tube circuit which comprises converting one of said radio frequency tubes into an audio frequency amplifierr In witness whereof, I hereunto subscribe my name this 4 day ofAug. 1931.

EMMETT FIN-LEY CARTER.

va biasing resistance associated with said de- 'tector. 

